Fabia tdi fornt windows wont work?

Hi all my farthers windows on his 07 fabia have stopped working. He took it to the skoda dealer and they found that the loom was damaged so they repaired the wires. They worked for a while now theyve stopped again. The dealer told him he may need a new ( modem ) and that this will need to be sync'd to the car?? Is this or does this sound about right? As they wanna charge about £300. This sounds like a lot of money any help is welcomed thanks